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Viaduct

One of the main engineering features of the Toowoomba Second Range Crossing is the viaduct, an 800m long bridge east of the New England Highway cutting that will negotiate the steep terrain of the range.

What was involved?

The viaduct was built using modern day construction technologies that consist of a jump form system for the individual bridge piers and a launching truss gantry for the installation of the Super T girder beams that will form part of the bridge deck.

Progress

Early works – completed

From May 2016, early works cleared the viaduct area by removing thick vegetation, establishing access tracks and preparing platforms for the piling works. A mobile concrete batching plant was also set up in the area to make concrete for the viaduct.

Piling – completed

Piling for the foundations of the piers of the viaduct was completed in January 2017. This consisted of drilling deep holes into the ground, which were then reinforced with steel cages and concrete. The piles are between six and 20m deep, depending on the section of the viaduct they are supporting. Once complete, the piles were capped with concrete. The piers, or bridge support structures, are then built on top of the piles.

Pier construction – completed

In October 2016, pier construction commenced, and will be completed in 2018. Piers are constructed in 4.5m lifts with a jump form technique that climbs up as each section is poured to a maximum height of 51m.

Headstocks – completed

Headstock construction commenced in December 2016. Headstocks are built on top of the piers to carry and support the bridge deck.

Bridge deck – completed

To complete the viaduct, the final stage is to construct the bridge deck. Constructing the bridge deck includes the installation of large precast concrete beams (Super T girders) and a number of large concrete pours.

The Super T girders will be installed using a launching truss gantry, which picks up the girders and positions them to be fed through to the back of the gantry. The gantry then ‘launches’ into its next position.